A new water supply source is needed for Irish Water's Eastern and Midlands Region.
Irish Water has published a report warning that demand for water in Dublin alone is set to increase by more than 50% by 2050.
The report points out recent water outages in Dublin cost the Irish economy more than €78m a day.
Irish Water's "Need Report" for the proposed Eastern and Midlands Region Water Supply Project, found that Ireland failed to adequately invest in water supply infrastructure for over half a century.
The report, which draws on extensive independent expert research, points out that saving water from conservation programmes and leakage reductions, won't be enough to deliver the quantities of water needed for future requirements.
It concludes that even after using the available water from existing sources, significant additional water will be required.
215 million litres a day extra will be needed by 2050 for the Dublin region alone.
A new source must be developed and utilised.
Irish Water has now begun an eight-week consultation process - and all the issues will be taken on board in preparing an Options Working Paper, which will be published later this year.
It is hoped a preferred option will be agreed, taking feedback into account, and submitted to An Bord Pleanala for planning approval in 2017.